Fix test/fixtures/docker-compose.yaml parse error

This is for the master branch (v1.0-alpha has already
been patched)

A parsing error was introduced in an earlier changeset.

FAB-1941

Change-Id: I56d99c812180d1b30554c376e0cf990a11b49602
Signed-off-by: Jim Zhang <jzhang@us.ibm.com>

test/fixtures/docker-compose.yml

@@ -2,12 +2,12 @@ version: '2.0'
 
 services:
 
- ca:
-   image: hyperledger/fabric-ca
-   ports:
-     - "7054:7054"
-   command: sh -c 'fabric-ca server start -ca /.fabric-ca/ec.pem -ca-key /.fabric-ca/ec-key.pem -config /etc/hyperledger/fabric-ca/server-config.json -address "0.0.0.0"'
-   container_name: ca
+  ca:
+    image: hyperledger/fabric-ca
+    ports:
+      - "7054:7054"
+    command: sh -c 'fabric-ca server start -ca /.fabric-ca/ec.pem -ca-key /.fabric-ca/ec-key.pem -config /etc/hyperledger/fabric-ca/server-config.json -address "0.0.0.0"'
+    container_name: ca
 
   orderer:
     image: hyperledger/fabric-orderer